How to reduce vblank/composition latency

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How to reduce vblank/composition latency

Wolfgang Grandegger

I use the following pipleline for live streaming:

  # gst-launch-1.0 -v udpsrc port=5678 buffer-size=2000000 do-timestamp=1 \
     caps="application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)JPEG, payload=(int)26, framerate=(fraction)30/1" \
     ! rtpjitterbuffer latency=5 \
     ! rtpjpegdepay \
     ! vaapijpegdec \
     ! vaapisink

I measure a glas to glas latency of approx. 100 ms. The pipeline itself
is responsible for only 40..50 ms latency. The rest is therefore from
the camera, network, display composition and the monitor lag.

I learned that the display vblank/composition latency is approx. 1.5/60
seconds for a 60 Hz monitor. How can I reduce that latency.  I'm using
the matchbox window manager [1] with X11. Is there a better choice or
configuration setting?

Switching to a 144 Hz monitor should then improve that latency
significantly. Does it scale with the frequency?


Thanks for any input,


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